Periodica Polytechnica (Budapest University of Technology and Economics)
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Evaluating Traffic Congestion at DHA Phase-I Roundabout: Level of Service Assessment and Development of Simulation Models Using PTV Vissim Software
Get PDFMost junctions, especially multilane roundabouts, are facing traffic congestion due to an increase in the number of vehicles traveling through Islamabad, Pakistan. This occurs when the amount of traffic demands more space than is available. In light of Pakistan's diverse driving conditions, the topic of effective vehicular traffic modelling is still heavily contested. Improving the traffic capacity of multilane roundabout is of great significance in solving the urban traffic problems. Considering the DHA Phase 1 roundabout situated at GT Road, this study aims to present a detailed analysis of the traffic delay at this roundabout. Highway Capacity Manual (HCM) and microscopic traffic simulation software PTV Vissim were used to analyze the traffic flow. Traffic Congestion Analysis of DHA Islamabad Phase-I roundabout was carried out by determining the Level of Service and developing a simulation model using PTV Vissim software. It was observed that LOS was improved from F to D. Delay was reduced by 94.18% at Fauji Foundation Hospital, 76.09% at DHA road, 70.85% at Kacheri road and 42.11% at Bahria road. Queue Length was reduced by 100% at Fauji Foundation Hospital, 73.75% at Bahria, 68.07% at DHA and 51.42% at Kacheri road. Moreover, a solution was proposed to decrease the traffic congestion and the LOS was significantly improved
Thermal Analysis of Simplified Railway Brake Blocks with Different Designs
Get PDFThe main problem with braking and stopping a railway vehicle is that the brake can heat up to a high temperature in a very short time. The dissipation of the generated heat is an important task, because the high thermal loads can cause cracks and deformation on the brake block. In this article, a simplified brake model is presented, on which both tribological experiments and finite element simulations were performed. The test results show good agreement with the heating conditions of real railway brake blocks on basis of literature. Microscopic examination of previously used real brake blocks clearly shows the different levels of heat load on the friction surface parts of the brake blocks. Instead of the currently used cast iron brake blocks, printed test specimens were made from metal powder material suitable for additive manufacturing. For better heat conduction, various shaped copper inserts were placed into the test specimen. It is also shown that if even a few percent of a material with good thermal conductivity are placed in the test specimen with appropriate geometry, the thermal conductivity of the test specimen can be significantly improved. Our goal is to use numerical simulation to find a geometric design that will most effectively remove heat from the higher temperature parts of the friction surface
Crude Oil Desulfurization by Polystyrene/Graphene Nanocomposite Membranes
Get PDFThe main aim of this paper is to evaluate the effect of graphene nanoplatelets (GNPs) on the desulfurization of the polystyrene nanofibers. Hence, different loadings of GNP, 0.5, 1, 1.5, and 2 wt.% GNP was incorporated into the polystyrene nanofibers using electrospinning technique. Several characteristics of the electrospun membranes were investigated. The obtained field emission scanning electron microscopy (FE-SEM) images confirmed the formation of uniform fibers and proper distribution of the particles in the electrospun structures. In addition, thinner fibers with smaller pore sizes were formed by addition of the GNPs into the nanofibrous mats. Moreover, the hydrophobic behavior reduced by increment of GNP content in the polystyrene nanofibers. Fourier transform infrared spectra (FTIR) confirmed the interaction of the polymer chains with the loaded filler particles. Furthermore, introduction of the GNP nanofillers in the decrease of the crude oil sulfur content from 2.8% to 2.6% via addition of 0.5 wt.% of GNPs into the as-spun fibers. Further reduction of the sulfur content (to 1.8%) was also obtained by embedding 2 wt.% of GNPs. Overall, the obtained data manifested that the electrospinning composite membranes are good candidate material for removing sulfur from crude oil
A Comprehensive Simulation Study of CdTe Energy Gap Effects on CdTe/CdS Solar Cell Characteristics: SCAPS-1D
Get PDFThe energy gap of the CdTe absorber layer in CdTe/CdS solar cells has a dominant effect on their performance. In this work, the effects of altering the energy band gap of CdTe (1.37 eV; 1.47 eV; 1.54 eV) on the features of the solar cell were analyzed using SCAPS-1D program. From our results, CdTe energy gap was found to be directly proportional to the open-circuit voltage (Voc), meaning that higher energy gaps gave higher Voc. But this was compensated by a fall in the short circuit current density (Jsc) due to light capture reduction effect which also contributes to the powering up of the cell. An appropriate energy bandgap of 1.47 eV for the CdTe layer has been calculated to secure high values of Voc and quite a high Jsc to increase overall conversion efficiency of the solar cell. Moreover, a noticeable trend appears in capacitance and conductance whereby smaller energy gaps yielded higher capacitance and conductance. The quantum efficiency was also changed; lower energy gaps had a better ability to absorb the photons and have higher efficiency to varying ranges of wavelengths. This study underscores the critical role of accurately tuning the CdTe energy gap during fabrication to optimize the efficiency of CdTe/CdS solar cells
A Detailed Fluid Mechanical Analysis on Pressure Relief Valve Blowdown
Get PDFWe study the root cause behind pressure relief valve blowdown, i.e. the difference in opening and reseating pressure. Simple disc valve geometries with an adjustment ring are studied, with and without a deflecting skirt on the valve body, for incompressible fluid. An analytical estimate is given for the fluid force acting on the valve body, which considers both the uneven pressure distribution and the momentum force due to fluid deflection, the former being the principal driving mechanism of blowdown. Computational Fluid Dynamics computations reveal that the flow is close to ideal and prove the validity of the assumptions behind the analytic results. It was found that the skirt deflecting the outlet flow is indispensable to generating blowdown; however, its role is not in the additional momentum force due to varying the exit jet angle of the flow, but in increasing the pressure at the outer radii due to its orifice effect
Pedestrian Safety and Distraction: A Contemporary Perspective
Get PDFThe present study, conducted in accordance with the PRISMA guidelines, aims to provide a contemporary perspective on the issue of pedestrian safety and distraction. The review was conducted using a systematic search strategy and included studies published between 2005 and 2022. A total of 250 studies were identified from the literature search on Google Scholar, EBSCO, Scopus, Web of Science etc., from which 30 studies were scrutinized for the final comprehensive study. The five study components considered for categorizing research papers were the frequency of mobile phone distraction, observational sites, performance measures, analysis methodologies, and other features related to mobile phone use among pedestrians. Most of the investigations were conducted in China and Australia. Numerous studies have examined factors like age and gender that may affect pedestrian behavior. The highest numbers of studies were conducted in 2022, 2021, and 2019, while the fewest studies were conducted in 2005, 2007, 2008, 2015, and 2017. Road junctions were the most common observation sites. Regression analysis was the primary method used in most of the studies. The review highlights the need for further research on this topic, particularly in the context of emerging technologies and changing pedestrian behaviors. Overall, the study emphasizes the importance of continued efforts to raise awareness and improve pedestrian safety in an increasingly distracted world
How Socioeconomic Status Differences Observable in Students' Delay of Gratification Evolved Over the Period of COVID-19-induced Online Education
Get PDFWe show the evolution of the delay of gratification (DG) in 950 students aged 10–14 during coronavirus-induced home-based online education, by analysing data from two waves of voluntary online surveys. Students in the highest SES category experienced an absolute increase in DG, whereas those in the lowest SES category suffered a decrease, resulting in a widening SES gap between the groups over a relatively short 30-day period
How Do Engineering Students Think About the Effects of Robotization of Working Conditions?
Get PDFResearch on the social and labour market impacts of robots increasingly emphasises the role of education in preparing future employees. This paper presents the results of a questionnaire-based survey conducted among engineering students. The survey was conducted using a measurement tool that was on the one hand partly developed in-house and on the other hand partly adapted from the General Attitudes Towards Robots Scale (GAToRS). The students (N = 320) expressed their views on the one hand how are their beliefs influenced by the experiences of robotisation they obtained in their studies or work? On the other hand what are their expectations regarding robotisation in the near future? The results indicate that they consider climate change, the scarcity of natural resources and the availability of fast and safe transport routes to be the factors that will have the greatest impact on human working conditions. The students see the role of expertise in Hungary changing in five years' time, with low-level skills being replaced by the need for specific competences. They believe that robots will create new working conditions and a new working culture that will replace physically demanding, dangerous and boring work. The survey also revealed that female students have stronger reservations and fears about robotisation than their male counterparts
Influence of Brick Waste Powder on the Shear Behaviour of Cemented Sandy Soil
Get PDFMany studies have proven that cement can be used effectively to treat unstable soils and improve their performance. This has led to an increased consumption of cement, already excessively used in the construction field. However, the use of cement in soil treatment is environmentally concerning, especially when applied on a large scale due to its significant contribution to CO2 emissions during the production process and its negative effects on the ecosystem and groundwater quality. To reduce the amount of cement consumed in the soil treatment process, its detrimental impact on the environment and its costs, alternative materials such as construction and demolition waste can be used as a complement to cement. This research aims to evaluate the effect of brick waste powder inclusion on the shear behaviour of cemented sandy soil. For this purpose, direct shear tests were carried out on different sand-cement-brick powder mixtures prepared at the dense state (Dr = 80%) with a water content of 10% and cured for 7, 14 and 28 days. The obtained results indicate an enhancement in the shear behaviour of the mixture in terms of maximum shear strength, cohesion and friction angle with increasing brick waste powder content. In addition, the increase of brick waste powder content enhanced the dilative behaviour of the cemented sand. Also, it is speculated through the experimental results that brick waste powder could potentially be used as a partial replacement of cement in soil treatment applications while ensuring similar or better shear strength characteristics
Fault-resilient Control Strategy for Cascaded Multilevel Inverters in Grid-connected PV Systems
Get PDFThis paper presents a fault-tolerant control strategy for a three-phase, seven-level Cascaded Multilevel Inverter (CMI) in grid-connected photovoltaic (PV) systems. The proposed approach enhances state-of-the-art CMI fault-tolerant control by integrating advanced compensation techniques, combining fault isolation and compensation, and conducting a comprehensive system analysis under fault conditions. The study focuses on improving power quality and system robustness, making it particularly suitable for modern grid-tied renewable energy applications. Compared to previous works, this research offers notable advances in power quality, system reliability, and fault resilience. Key innovations include optimizing the use of renewable energy in large-scale solar installations through multilevel inverter technology and addressing operational faults to ensure uninterrupted power delivery. The findings underscore the significance of robust fault-tolerant strategies in improving the performance and stability of renewable energy systems